Wave data recording program Dunk Island 1998–2002 Coastal Services data report No. W2004.2 ISSN 1449–7611 Abstract This report provides summaries of primary analysis of wave data recorded in water depths of approximately 20m relative to lowest astronomical tide, 12.7km north of Dunk Island and 8km northeast of Clump Point in north Queensland. Data was recorded using a Datawell Waverider buoy, and covers the periods from 18 December 1998 to 12 November 2002. The data was divided into seasonal groupings for analysis. No estimations of wave direction data have been provided. This report has been prepared by the EPA’s Coastal Services Unit, Environmental Sciences Division. The EPA acknowledges the following team members who contributed their time and effort to the preparation of this report: John Mohoupt; Vince Cunningham; Gary Hart; Jeff Shortell; Daniel Conwell; Colin Newport; Darren Hanis; Martin Hansen and Jim Waldron. Wave data recording program Dunk Island 1998–2002 Disclaimer While reasonable care and attention have been exercised in the collection, processing and compilation of the wave data included in this report, the Coastal Services Unit does not guarantee the accuracy and reliability of this information in any way. The Environmental Protection Agency accepts no responsibility for the use of this information in any way. Environmental Protection Agency PO Box 155 BRISBANE ALBERT ST QLD 4002. Copyright Copyright Queensland Government 2004. Copyright protects this publication. Apart from any fair dealing for the purpose of study, research, criticism or review as permitted under the Copyright Act, no part of this report can be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without having prior written permission. Direct enquiries to the Manager, Publishing Services, PO Box 155 BRISBANE ALBERT STREET QLD 4002. Cover photo: View from the Dunk Island Waverider buoy location, looking north towards the Barnard Islands and the Queensland coastline (see figure 1). Wave data recording program - Dunk Island 1998 to 2002 1 May 2004y ISSN 1449–7611y Coastal Services data report No 2004.2 Contents 1.0 Introduction 2.0 Recording equipment configuration 3.0 Laboratory calibration checks 4.0 Wave recording and analysis procedures 5.0 Data losses 6.0 Data presentation 7.0 References 8.0 Other reports in this series 9.0 Details of wave recorder installation Tables Table 1: Dunk Island wave climate summary of data capture December 1998–November 2002 Table 2: Queensland cyclones 20 January 1999–5 March 2002 Table 3: Major meteorological events 11 February 1999–12 April 2002 Table 4: Wave period (TP)/wave height (Hsig) occurrences, all data, all directions, in days Table 5: Wave period (TP)/wave height (Hsig) occurrences, summer data, all directions, in days Table 6: Wave period (TP)/wave height (Hsig) occurrences, winter data, all directions, in days Table 7: Wave period (TP)/wave height (Hsig) occurrences, all data, all directions, in percentage occurrences Table 8: Wave period (TP)/wave height (Hsig) occurrences, summer data, all directions, in percentage occurrences Table 9: Wave period (TP)/wave height (Hsig) occurrences, winter data, all directions, in percentage occurrences Figures Figure 1: Locality plan – Wave data recording program Dunk Island Figure 2: Percentage (of time) exceedance of wave heights (Hsig) for all wave periods (Tp) Figure 3: Histogram percentage (of time) occurrence of wave heights (Hsig) for all wave periods (Tp) Figure 4: Histogram percentage (of time) occurrence of wave periods (Tp) for all wave heights (Hsig) Figure 5: Wave parameter relationships Figure 6.00: Daily wave recordings 1 January–31 December 1998 Figure 6.01: Daily wave recordings 1 January–31 December 1999 Figure 6.02: Daily wave recordings 1 January–31 December 2000 Figure 6.03: Daily wave recordings 1 January–31 December 2001 Figure 6.04: Daily wave recordings 1 January–31 December 2002 Figure 7: Whole recording period wave recordings 18 December 1998–12 November 2002 Figure 8: Cyclone tracks 18 December 1998–12 November 2002 (for all cyclones in table 2) Figure 9: Zero up-crossing analysis Figure 10: Monthly average wave heights (Hsig) Appendices Appendix A: Glossary of terms Wave data recording program - Dunk Island 1998 to 2002 2 May 2004y ISSN 1449–7611y Coastal Services data report No 2004.2 1.0 Introduction The Coastal Services Unit, as part of its long-term data collection program, has maintained a network of wave recording stations along Queensland’s coast since 1968. This report summarises the primary analysis of wave data collected at the Dunk Island station. In addition, brief details of the recording equipment, the methods of handling raw data and the type of analyses employed are provided. The Dunk Island wave recording station was commissioned as a project to study cyclonic wave conditions by the Environmental Protection Agency (EPA). As an overview of the EPA’s coverage of data recording along the Queensland coastline, the wave recording stations have been grouped into three categories and are shown below: Permanent sites: These sites form part of long-term data collection activities along the Queensland coast that collect wave statistics used for coastal management purposes. The stations are fully funded and operated by the EPA Project sites: These sites are of limited duration, associated with some specific coastal activity, and are used to assess wave conditions for coastal investigation projects and/or to help monitor works such as beach nourishment. The stations are fully funded and operated by the Environmental Protection Agency as specific projects. Joint project sites: The life of these sites will vary in duration, and they are associated with specific projects, to assess wave conditions, or to monitor works. These stations are operated in conjunction with (and jointly funded by) other agencies. The 2003 site groups are as follows: Active wave recording stations–2003 Permanent Project Joint project Joint project partners Brisbane Woorim Tweed Heads TRESBP♣ Mackay Moreton Bay Gold Coast Seaway GCCC+ Townsville Mooloolaba Hay Point PCQ # Cairns Weipa PCQ # Emu Park Caloundra PoBC♦ ♣ Tweed River Entrance Sand Bypassing Project (joint project of Qld and NSW governments with support of GCCC) + Gold Coast City Council # Ports Corporation of Queensland ♦ Port of Brisbane Corporation 2.0 Recording equipment configuration The Coastal Services Unit’s wave recording program utilises either of two systems to measure wave data: the Waverider buoy system or a wave pole. For the period covered by this summary report the Waverider system was utilised to measure the sea surface fluctuations at the Dunk Island site. Directional and non-directional Waverider buoys measure vertical acceleration by means of an accelerometer that is mounted on a gravity-stabilised platform suspended in a fluid-filled plastic sphere located at the bottom of the buoy. This data is twice integrated to give displacement. The instantaneous water level and directional data (if present) are transmitted to the shore recording station as a frequency- modulated high frequency radio signal. Both directional and non-directional buoys are in operation but only a non-directional buoy was used at Dunk Island. The Dunk Island station was first installed on 18 December, 1998, and consisted of a shore station and Waverider buoy. The shore station used a personal computer (PC) system linked to the Datawell DIWAR Waverider receiver/digitiser. The changing water level was digitised at a rate of 0.39sec intervals (2.56Hz) and recorded in bursts of 4096 data points (approximately 26min of data). Each record was stored on the hard disk of the PC. Proprietary software running on the PC controlled the timing of the data recordings and Wave data recording program - Dunk Island 1998 to 2002 3 May 2004y ISSN 1449–7611y Coastal Services data report No 2004.2 processed the data in ‘near real time’ to provide a set of standard sea-state parameters and spectra. Recorded data and analysis results were then accessed remotely via the public telephone network and downloaded daily to a central computer system in Brisbane for further checking, processing and archiving. Further information on the operation of the Waverider buoy and the recording systems may be obtained from the sources listed in section 7.0 of this report. 3.0 Laboratory calibration checks Waverider buoys used by the Coastal Services Unit are calibrated before deployment and also after recovery. Calibration is performed at the EPA’s Deagon site using a buoy calibrator to simulate sinusoidal waves with amplitudes of either 1m or 1·4m depending on whether a 0·7m or 0·9m diameter buoy is being tested. The wheel is electrically controlled and the frequency may be varied from 0.016–0.25Hz. It is usual to check three frequencies during a calibration. The following characteristics of the buoy are also checked during the calibration procedure: • phase and amplitude response; • accelerometer platform stability; • platform tilt; • battery capacity; • power output. When the buoy was recovered from Dunk Island, laboratory calibration checks for accelerometer error and platform tilt were performed on the buoy. The results of these checks were within the manufacturer’s specifications and so no adjustments to the recorded data were made. 4.0 Wave recording and analysis procedures Between 18 December, 1998, and 14 November, 2002, wave data was